Don't know if the following applies to the benchmarks, but I just learned that indices in PG always grow in size, ie. the entries for deleted rows are not removed, not even by VACUUM. This is apparently the penalty for being able to do a VACUUM on a live db.
The unofficial way of thoroughly cleaning up a PG db is to first do a VACUUM, then dropping indices and subsequently recreating all of them. Wether this can be done on a live db depends on the given application.
Has anyone using OpenACS had to deal with these issues? Apparently heavily used PG db's use a cron job to thoroughly purge the empty space at regular intervals, including recreating all the indices.
Frank.
